1. Field of the Invention
This invention relates to micro manipulation, and more particularly to a method for optically micro-manipulating a microscopic specimen, such as a tissue cell, a cell organelle or the like, without mechanically touching the specimen, and also to an optical micro-manipulator for realizing the method.
2. Description of the Related Art
It is difficult to forming an image of a microscopic specimen viewed in a desired direction, by the use of a general optical microscope, since the microscope has various limitations in optical design.
In the case of an optical microscope of a general structure, a microscopic specimen is placed on a mechanical stage located perpendicular to the optical axis of the microscope, and an image of the microscopic specimen is formed on a surface parallel with the stage.
This microscope has rough and fine mechanical-stage controls and rough and fine focus-adjustments.
The mechanical-stage controls can move the mechanical stage in a horizontal plane (X-Y plane) perpendicular to the optical axis (Z-axis) of an objective lens, to thereby set within the field of view a desired portion of a microscopic specimen in the X-Y plane.
The focus adjustments move the mechanical stage in a direction of the optical axis so as to obtain a good focal point. Thus, these adjustments cannot be used, in a usual manner of use, to microscopically examine a microscopic specimen in a plane parallel with the optical axis (i.e., an X-z plane or a Y-Z plane).
A microscopic specimen such as a cell organelle, which is immersed in a liquid medium, typically, a physiological salt solution, is microscopically examined, while fixed with a cover glass on a slide glass. Accordingly, the specimen can be microscopically examined only from above the cover glass. Once fixed, the specimen is hard to microscopically examine in another direction.
There is a known mechanical micro-manipulator for micro-manipulating a specimen under a microscope so as to permit the specimen to be microscopically examined in a desired direction.
This micro-manipulator is used in combination with such a mechanical stage for a microscope as is described above, and has a tool for micro-manipulation, such as a microscopic probe or a hold pipette, which is movably placed on the mechanical stage.
A liquid medium in which a microscopic specimen is soaked is placed on the mechanical stage at the tips of the manipulation tool.
The hold pipette consists of a hollow tube member of a small diameter made of, e.g., glass. A fine pressure regulator, which is connected to the hold pipette, sucks the liquid medium contained in the hold pipette to enable the tip of the pipette to trap the specimen.
The manipulation tool can be moved in the directions of the X-, Y- and Z-axes by hydraulic control or electric control with the use of a remote controller.
The remote controller has manually-operated elements such as a joystick, a push button, etc. The observer can slightly move the manipulation tool in a desired one of the X-, Y- and Z-axis directions, by manually operating the remote controller, so as to set the tool in a desired position. As a result, the specimen can be micro-manipulated on the mechanical stage.
In order to perform desired fine movement of the manipulation tool, however, it is necessary to accurately operate the manual elements of the remote controller, and a skilled technique is required for the accurate operation. Actually, such a skilled technique is hard to obtain.
Further, when a hard manipulation tool mechanically manipulates such a soft microscopic specimen as a cell organelle, it can easily deform or damage the specimen.
In summary, it is very difficult to permit a specimen to be microscopically examined in a desired direction, with the use of a general microscope. In order to overcome this difficulty, it is not preferable to use the above-described conventional mechanical micro-manipulator, since the specimen may be adversely affected by mechanical contact, as well as the operational difficulty of the manipulator.